In a general chemical process, heat exchange is performed in various paths through a reactor or a distillation column, and waste heat generated after the heat exchange may be reused or discarded. For example, as shown in FIG. 1, when the waste heat is a low-grade heat source in the state of a sensible heat of about 70° C. or more, for example, 70 to 90° C., a temperature is too low to substantially reuse, and thus the waste heat of condensation by condensate water is discarded.
Meanwhile, steam is used for various purposes in industrial fields, and particularly, in the chemical process, high temperature steam is mainly used. The high temperature steam is generally heats water in atmospheric pressure and room temperature states to the evaporation point thereof, and high pressure is applied to the water turned to steam to increase internal energy, thereby generating the high temperature steam. Here, a large amount of energy is required to be consumed to evaporate water in a liquid state.